carrier pigeon

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A homing pigeon, especially one trained to carry messages.
2. n. Any of various large domestic pigeons having a prominent wattle.

Century Dictionary and Cyclopedia

1. n. A pigeon of a particular breed trained to convey from one place to another written messages tied to the neck or wing, or more commonly to the leg. The destination of the message must be some point near the pigeon's home, whither it will fly back from any place to which it has been carried; hence it is also called the homing-pigeon. The distance from which it will return to its home, when in perfect condition, may be a thousand miles or more.
2. n. A breed of domesticated pigeon, having as its most apparent characteristic a huge wattle, like a miniature cauliflower, about the base of the stout beak, and a small wattle around the eye. The skull is narrow, the general build slender, and the length about 17 inches. The favorite color is solid black or dun; but there are silver and blue breeds. This breed does not carry messages, being bred for points only; not only does the bird fly indifferently, but its sight is partly obscured by the wattles. The birds used during the Franco-German war were largely Antwerps, and the birds now trained for long-distance flights are homers.

Wiktionary

1. n. A domestic pigeon which transports attached messages or very small parcels from the place where it is released to a familiar destination.

GNU Webster's 1913

1. n. (Zoöl.) a variety of the domestic pigeon used to convey letters from a distant point to to its home.

WordNet 3.0

1. n. a homing pigeon used to carry messages